[R-390] Ballastubes

[Drew Papanek]

Walter Schulz  <k3oqf at localnet.com> wrote:

>Does anybody know where I can find Ballast tubes for my R-390A/URR? Sure 
>would appreciate any >advice on this.

Walter,

You've by now seen the high price quotations for the 3TF7 ballastube, making 
modifications to
replace that tube attractive.

I suggest you go to r-390a.net.  Click on references, Pearls of Wisdom.  
There you will find  a wealth of information (and controversy!) regarding 
that R-390x topic and others, all gleaned from this forum over the years.  
Thanks go to Wei-i Li for his untiring compilation efforts!

I personally like and use the "Two 12BA6 and a paperclip" mod whereby the 
6BA6's used in PTO and BFO are replaced with 12BA6's and then the ballastube 
socket is jumpered out (a piece of paperclip
works well).  The mod is extremely simple, inherently reversible, and 
dissipates less heat  than the
various modifications or even the stock configuration.

One mod mentioned is Dr. Jerry's simple AC current regulator.  I can e-mail 
you the schematic and notes.

Drew

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